Biogeography of Amazon Palms

Abstract In this chapter, I first bring together the physical factors of the Amazon environment (soils, climate, river systems, topography) and interpret them in relation to palm distributions; that is, I take an ecological biogeography approach. Then I consider geologic history and its relation with palms; that is, I take a historical biogeographic approach, with particular reference to the refuge theory. The main difference between these two approaches is one of scale. The ecological approach is useful at the small scale, whereas the historical biogeographic approach considers distributions on a larger scale. The biotic factors that form part of the ecological biogeography, such as dispersal and dispersers, are discussed as well.Few palms are restricted to any one soil type. Widespread species such as Mauritia flexuosaalmost always occur on inundated soils, but these can be gleysols, solonchaks, or fluvisols. Certain palms are perhaps more abundant on specific soil types, but can also occur on others. For example, Lescure and colleagues (1992) found that Leopoldinia piassabawas common on podzols, but also occurred, less abundantly, on other soils. At the small scale, soils are a mosaic of types. For example, Jordan (1989) showed how small variations in topography, which affected the water table, could change soil type over a short distance, with a consequent effect on vegetation. Within a 500 m transect, with an 8 m elevational range, six different communities and associated soil types occurred. Locally, palm distribution is closely tied to both soil type and drainage, as clearly shown by Kahn and de Granville (1992).